Students could discuss the differences between the root hair cell and a typical plant cell, explaining why the root hair lacks features such as chloroplasts and why it needs the root hair. This could then be used as an introduction to the concept of surface area. Pupils could investigate the concept by drawing the cross-section of the root and then drawing another without the root hairs. They could also measure the surface area of each of the roots with string to demonstrate how the hairs increase the area available for the uptake of water and minerals.